Synthesis, thermal characterization and local structure studies of Gd doped Th0.7U0.3O2 using X-ray absorption spectroscopy

Abstract

(Th_0.7−xU_0.3Gd_x)O_2+y microspheres where x = 0, 0.05, 0.10 and 0.15 were prepared by internal gelation method. Good quality translucent microspheres of size ∼1.70 to 2.0 mm were obtained when low metal ([M]) and high [hexamethylenetetramine + urea]/[M] (R) concentration was used. The solid solutions prepared from these microspheres were subjected to thermal expansion studies which showed a gradual decrease in thermal expansion coefficient values with increase in Gd ion concentration. Specific heat capacities of mixed oxides were measured from 300 to 850 K and showed that the temperature dependence of the heat capacities of Gd doped samples is similar to that of the un-doped sample. The local structure studies by EXAFS showed that Gd–O, Gd–Th and longer Gd–O paths are similar to Th–O, Th–Th and longer Th–O path lengths. EXAFS studies showed higher oxygen coordination in the case of the 10% Gd substituted sample compared to the other samples.